The exemplary embodiments described herein relate to dry cement blends that include inert microparticles that produce cement slurries with a lower viscosity and a longer aging window, and methods relating thereto.
Settable compositions (e.g., cement slurries) are widely used in relation to the exploration and production of fluids from subterranean formations. For example, cement sheaths are used to support the wellbore. Also, cement plugs are used for isolating zones of a subterranean formation and for plugging the wellbore altogether when abandoned.
Cement slurries are often prepared at the well site just before performing a cementing operation because aging of the cement slurry causes the viscosity to rise to a point that the slurry is unpumpable. As used herein, a fluid is considered to be in a pumpable fluid state where the fluid has a viscosity of less than 70 Bc, as measured using an API approved HPHT (high pressure high temperature) cement consistometer, such as a FANN Model 165AT (available from FANN Instrument Company) at 140° F. (60° C.). Mixing of cement slurries at the well site requires mixing equipment and bulk storage for the components of the settable composition. Further, it requires transporting individual components to the well site. Equipment costs, transportation expenses, and cost of additional labor required to transport the equipment and to operate it can be high, especially when considering these expenses are incurred at every well site.
To mitigate these costs, extended life settable compositions have been developed to allow for a broader aging window (i.e., the time frame that the cement slurry is pumpable and suitable for use in cementing operations). The broader aging window allows for mixing of the cement slurry at another location and transporting it to the well site. Therefore, a single mixing location can be used for multiple well sites. Alternatively, the flexibility of preparing the slurry at the well site, days or weeks before it is needed provides opportunity to increase equipment and labor efficiencies. Additional expansion of this aging window and further reduction in the viscosity of cement slurries would be of additional value to those skilled in the art.